Mount it so that the water pump shaft points to the center of the fan motor and as close to the motor as possible front and rear. A couple of stock rubber cooling hoses will help you position it. No need to put the radiator in a custom place and then have to jump through hoops to run hoses to it. Use stock stuff when you can. Don't forget the spring in the lower hose to prevent it collapsing and shutting off supply to the motor.

Are all stock radiator hoses the same length on a small block 350? I know that must sound like a dumb question, but I had to ask.